I read to put phone books under the legs of the crib (in our case our pack in play) until you reach the desired incline. Although reluctant at first as I was afraid they would fall. It worked like a charm. We had no sliding issues with it but we did keep it wedged between two walls and the bed so three of the four sides were tightly held in place. HTH

Oh I also read if you have a co-sleeper playpen. They make the extension legs for higher beds and you can put the legs on just one side to give the desired incline.

I would be careful with wedges if your baby moves around I would worry that they would get caught and could risk suffocation. Just a thought...

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[SIZE="3"]Megan, Wife to Ron, Mommy to Ben 5-7-09, Grant 4-22-10Abby 6-16-12,Alex 6-15-15 You're so beautiful to think of, but so hard to be without, E no longer in our home, always in our heart